Microbiologically Influenced Corrosion (MIC) is a significant problem within the oil and gas industry. It is estimated that as many as 20 to 30% of pipeline corrosion failures may be attributed to MIC. MIC is usually defined as a specific type of corrosion influenced by the presence or activity of microorganisms including bacteria and fungi. The primary pathway by which MIC occurs is via development of a community of microorganisms on a surface such as a pipe within an organic matrix commonly referred to as biofilm.
Biofilm consists of cells immobilized in a substratum, frequently embedded in an organic polymer matrix of microbial origin, which can restrict the diffusion of substances and bind antimicrobials. It is estimated that more than 99% of all the planet's bacteria live in biofilm communities. In flowing aquatic environments, a biofilm consists of a sticky and absorptive polysaccharide matrix encompassing microorganisms. Biofilm bacteria are morphologically and metabolically distinct from free-floating bacteria. Their structural organization is a characteristic feature and distinguishes biofilm cultures from conventional planktonic organisms.
One of the most important strategies in mitigating MIC is the removal of biofilm or prevention of biofilm formation. However, control of biofilms and sessile bacteria is much more difficult to achieve than control of planktonic cells, primarily due to the presence of the exogenous polymeric matrix. This is due, in part, to the dynamic nature of biofilms, whereby biofilms continuously change in thickness, surface distribution, microbial populations and chemical composition, and respond to changes in environmental factors such as water temperature, water chemistry and surface conditions. Thus, the complexity of biofilms reduces the effectiveness of typical chemical treatment and removal strategies.
This reduced efficacy is evidenced by the typically much higher concentrations of chemical biocides required for biofilm removal and control relative to control of planktonic organisms. This can increase both the cost of treatment and may also add an additional concern of corrosion due to extraordinarily high concentrations of corrosive chemical biocides.
In this regard, several biocides are used for MIC control in oil field gathering lines. Commonly used biocides are non-oxidizing chemicals such as glutaraldehyde or bis[tetrakis(hydroxymethyl)phosphonium] sulfate (THPS). Some concern has arisen that these biocides may be inherently corrosive at high end use concentrations and could cause general corrosion in the assets they are protecting from MIC.
Another group of biocides used in industry are quaternary amines. However, quaternary amines used alone at reasonable and affordable treatment concentrations are generally not as effective as other biocides in controlling microorganisms attached to metal surfaces and bulk fluids.
In view of the above, a need exists for an improved composition for preventing and inhibiting biofilm growth in industrial systems, particularly in oil field applications.